In recent years, a variety of electronic devices such as a PC (Personal Computer) and a PDA (Personal Digital Assistant) have increasingly adopted an image pickup function, in addition to original functions of the device. The electronic device having the image pickup function is mounted thereon with a small image pickup module. The image pickup module includes an optical system having a plurality of optical components such as a focus lens and the like, an actuator that moves the optical components so as to perform a zoom adjustment operation and an image pickup element that generates an image signal by photoelectrically converting a subject image, which is imaged by the optical system.
As the actuator, a lens drive mechanism having a voice coil motor (VCM) that is formed by mounting a magnet (a permanent magnet), a yoke and a coil at an outer periphery of the optical system has been suggested. In the lens drive mechanism, the lens is moved in an optical axis direction by the VCM, so that a focusing operation is performed.
The VCM of the image pickup module that is used for a mobile phone controls a focus position of the lens by an amount of current that is supplied to the coil. In general, at a state where the current is zero, the focusing is made at infinity and at a state where the maximum current is supplied, the focusing is made at a closest point. However, when it is intended to continuously focus on a closest subject, it is necessary to continuously supply the maximum current to the VCM, so that the power consumption may be increased. Accompanied by this, a dark current due to heat generation of the image pickup element is increased, so that an image quality may be deteriorated.
Also, while the power consumption that is necessary in the image pickup module tends to increase, demands for miniaturization/high performance of the electronic device is increasing year by year. For this reason, a technology of attempting the low power consumption while maintaining a size of the electronic device as it is by appropriately changing a control mode within a range of allowed power consumption (refer to Patent Document 1) and a technology of detecting a current temperature of the electronic device to thus switch the electronic device to a control mode corresponding to a using status of the device have been suggested.
Patent Document 1: Japanese Patent Application Publication No.: 2005-130045A
Patent Document 2: Japanese Patent Application Publication No.: 2006-115250A
However, the control disclosed in Patent Documents 1 and 2 is to switch signal processing of a drive signal of the image pickup element or a picked-up image and does not directly control the heat generation of a heat generation source. For this reason, although the power consumption can be suppressed, an effect of suppressing the heat generation is low and the increase of the dark current due to the temperature increase cannot be suppressed. Also, even when image information is corrected in post processing, it is difficult to perfectly restore the image information of a high grade.
Therefore, an object of the invention is to provide an image pickup module capable of optimally drive-controlling a lens drive unit in accordance with a use of a picked-up scene or an output image signal to thus suppress heat generation of the lens drive unit, thereby improving an image quality of a picked-up image.